Compressor stator vane

ABSTRACT

A vane unit system having a plurality of vane units having at least one air foil projecting from a base. The base has a hole which receives a pin which extends between adjacent bases of vane units therein forming a rigid ring of vanes that are less susceptible to vane motion caused by pressure fluctuations within the compressor of a gas turbine. A blade assembly tool having a shape to fit within the slot in a casing that receives the vane units allows for the installation of vane units with interlocking pins without the necessity of having to remove the rotor from the casing.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/358,931 filed Feb. 22, 2002, the contents of which are incorporatedherein by reference in their entirety.

BACKGROUND OF THE INVENTION

Compressor stator vanes in an industrial gas turbine are loaded andunloaded during start-stop cycles. In addition, the vanes are subject tosmall pressure fluctuations during operation. These result in relativemotion between the vane base and the casing in which the vanes areassembled. The relative motion results in wear of both the vane base andcasing, which, in turn, results in loose vanes. An example of the wearpattern on the base of a vane unit and in particular on a projection onthe contact surface is shown in FIGS. 17A and 17B. The loose vanesbecome more susceptible to relative motion and begin to chatter.Expensive repair or replacement of the vanes and case does not solve thewear and chatter problem; it simply begins the process anew. Repairand/or replacement of the vanes and casing is expensive.

SUMMARY OF THE INVENTION

This invention relates generally to a compressor having a casing havingat least one slot. The slot has a pair of side edges wherein each sideedge has a groove. A plurality of vane units each have base and airfoilvane projecting from the base. The base has a pair of holes. A pinextends between the holes in adjacent bases of the vane units forforming a ring from a plurality of vane units.

In one embodiment, at least one shim is interposed between a pair ofadjacent vane units, the shim having a hole through which the pinbetween the adjacent vane units extends.

In one embodiment, the pin is a slotted spring pin having a hollowcylindrical tube having a longitudinal slot. The cylindrical tube haschamfered ends.

A compressor has a rotor having a plurality of blades and a casing forencircling the rotor. The casing has at least one slot for retaining aplurality of vanes. Each vane unit has a base and at least one airfoilvane projecting from the base. A coupling device extends betweenadjacent bases for forming a ring unit from a plurality of vane units tostiffen the airfoil vanes.

In one embodiment, the coupling device is at least one pin extendingbetween holes in adjacent bases. The pin is a slotted spring pin havinga hollow cylindrical tube having a longitudinal slot. In anotherembodiment, the coupling device is a projection on one base received bya hole on the adjacent base. In alternative embodiment, the couplingdevice is a groove on one vane unit for receiving a tongue on anadjacent vane unit.

A repair kit for repairing a compressor includes a device for placing ahole in a base of a vane unit, a device for inserting a pin into thehole of the base, and a blade assembly tool for positioning andconnecting adjacent vane units.

The blade assembly tool has a main portion having a pair of face edgesand a pair of side edges. The main portion has a curvature and a widthfor receipt of the pair of side edges by a slot in a casing. The toolhas a pair of contact blocks. Each contact block is secured to one ofthe face edges.

In one embodiment, the contact blocks have a width for fitting between apair of side walls of the slot, The main portion has a pair of holes anda series of scribe lines.

A method of repairing at least one loose stator vane includes the stepof securing at least one vane unit to another vane unit for stiffeningthe vane units.

In an embodiment, the method includes securing at least one vane unit toanother vane unit by connecting the plurality of vane units to eachother by a plurality of pins.

In an embodiment, the base of the vane unit has a base having a pair ofmounting surfaces and a pair of engaging surfaces. A hole is drilled inat least one of the engaging surfaces for receiving one of the pins forconnecting to another engaging surface of another vane unit.

A method of repairing of a compressor further includes the step ofremoving the existing the vane units from the casing of the compressor.The holes drilled into the base of the vane unit are drilled into thebase of the vane units while they are removed from the casing.

A method of repairing of a compressor includes the step of positioning avane unit at the dead center of the casing. At least one assembly toolis slid in the slot by placing the edges of the assembly tool in thegrooves in the slot. The tool engages the vane unit with the contactblock for maintaining the second vane unit with a pin projecting fromthe engaging side of the base is slid into the slot with the projectionof the mounting edge received by the groove in the slot. The pin isdriven into the hole on the engaging edge of the base of the first vaneunit by sliding at least one assembly tool in the slot by placing theedges of the assembly tool in the grooves in the slot and engaging thevane unit with the contact block and driving the second vane unittowards the first vane unit.

The method of repairing of a compressor further includes removing of theassembly tool in engagement with the second vane unit. Another vane unitwith a pin projecting from the engaging side of the base is slid intothe slot with the projection of the mounting edge received by the groovein the slot. The pin is driven into the hole on the engaging edge of thebase of the previous vane unit by sliding at least one assembly tool inthe slot by placing the edges of the assembly tool in the grooves in theslot and engaging the vane unit with the contact block and driving theanother vane unit towards the previous vane unit. The process isrepeated until the vane units fill the slot in the casing.

The method of repairing a compressor also includes the step in oneembodiment of interposing at least one shim between adjacent vane unitsfor positioning one of the engaging edges of a vane unit flush with theedge of the casing.

A compressor has a rotor having a plurality of blades and a casing forencircling the rotor. A plurality of vane units each having a base andat least one airfoil vane projecting from the base. The casing has atleast one slot for retaining the vanes and an air extraction slot. Theair extraction slot underlies the slot and defines a casing hook. Acoupling device extends between adjacent bases for forming a ring unitfrom a plurality of vane units to stiffen the airfoil vanes. At leastone bracket is carried by one vane unit engaging the casing hook.

In one embodiment, the coupling device is at least one pin extendingbetween holes in adjacent bases. The pin is a slotted spring pin havinga hollow cylindrical tube having a longitudinal slot. The cylindricaltube has chamfered ends.

In an embodiment, the bracket is secured by a fastener extending throughthe casing and to the base of the vane unit.

A stator vane system has a casing having a curved inner surface and apair of joint surfaces for mounting with at least another casing forencircling a rotor of compressor. The casing has at least one slot. Theslot extends from one joint surface edge to the other joint surface. Theslot has a bottom and a pair of side edges. Each side edge has a grooveextending from one joint surface to the other joint surface and caninclude an air extraction slot. The air extraction slot underlies theslot and defines casing hook joint surface.

A plurality of vane units each having a base and airfoil vane projectingfrom the base. The base has a pair of mountings sides opposite eachother and each having a projection receivable by the groove in the slotfor retaining the vane unit, and a pair of engaging edges opposite eachother for engaging adjacent vane units. Each vane unit has a hole ineach engaging edge. A pin extends between the holes in adjacent bases ofthe units for damping the movement of the vane. In a preferredembodiment, a bracket is carried by one of the vane units.

The invention is a means for modifying a set of compressor stator vanesfor an industrial gas turbine so as to avoid wear of the vane base andreduce chatter. The vanes are joined by a simple mechanical means suchthat the discrete vanes form a rigid ring of vanes and are lesssusceptible to individual vane motion caused by pressure fluctuations.

The vanes, according to the invention, result in changing the reactionpoints on the vane base. The relative motion between the vane base andthe supporting case is greatly reduced.

The vane units in a preferred embodiment can be installed into existinggas turbines using prior art vanes during the gas turbine overhaulcycle. The vane units according to the invention require less repairand/or replacement of the vanes and/or the casing than the prior artvanes.

The objective of the invention is to change the load distribution on thevane base without altering the fit or function of the vane. The vanesare connected (coupled) by use of a slotted spring pin so that thetangential pressure load on the vane is opposed by the spring pin anddoes not cause tangential displacement of the vane base. The vanes areconnected such that they form a rigid ring of vanes and do not moverelative to one another when acted upon by pressure fluctuations. Thefrictional force produced by the spring pin acts in opposition to theaxial gas load and prevents, or at least reduces, axial motion of thevane.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1A is a schematic of a gas turbine;

FIG. 1B is a exploded perspective view of a compressor section of thegas turbine;

FIG. 2 is a front view of a plurality of compressor stator vanesassembled in the casing;

FIG. 3 is a side view of the casing;

FIG. 4A is a perspective view of a vane unit, according to thisinvention;

FIG. 4B is a plan view of a spring pin;

FIG. 5A is an enlarged view of the edge of the casing showing the fifthstage;

FIG. 5B is an enlarged view of the edge of the casing showing theseventh stage;

FIG. 5C is an enlarged view of the fourth stage;

FIG. 6 is an exploded view of a pair of vane units and an interposedspring pin;

FIG. 7 is side front perspective view of a pair of vane units assembledtogether;

FIG. 8 is a sectional view of a plurality of vane units in the casing;

FIG. 9 is a side view of a shim;

FIG. 10A is a side view of the casing with shims protruding;

FIG. 10B is a front view of the fifth stage in the casing with a missingshim;

FIG. 11 is a sectional view of the casing with vane assembly and shims;

FIG. 12 is a side perspective view of a shim carried by a pin adjacentto a pair of vane units;

FIG. 13 is a side perspective view of a drill fixture;

FIG. 14A is a front view of an assembly tool;

FIG. 14B is a side view of the assembly tool;

FIGS. 15A-15C are top, front, and side views of a prior art vane unitshowing the reaction forces;

FIGS. 16A-16C are top, front, and side views of a vane unit according tothe invention showing the reaction forces;

FIGS. 17A and 17B are front views and bottom views of a prior art vaneunit.

FIG. 18 is a side view of an alternative compressor;

FIG. 19 is a side view of a portion of a casing with an alternative vanesystem;

FIG. 20 is a top view of vane unit with holes shown in hidden line; and

FIG. 21 is an exploded view of a pair of vane units with a tongue andgroove.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings in detail, where like numerals indicate likeelements, there is illustrated a vane system including a vane unit inaccordance with the present invention designated generally as 20.

Gas turbines are used in various locations such as aircraft, ships, andin power plants. Referring to FIG. 1A a schematic of a gas turbine 24 isshown. The turbine 24 has a compressor section 26 that compressesatmospheric air prior to the air being mixed and combusted with a fuel,i.e., gas, in a combustion chamber 28.

The turbine 24 has a turbine section 30 that converts the energy of thecompressed heated air to rotation energy. The turbine section 30 istailored differently depending on the purpose of the turbine. In a powerplant scenario, the turbine section 30 of the gas turbine 24 has twoportions. One portion 32 drives a shaft 34 to the compressor section 26and the second portion is a power turbine 36 for driving a generator 38.

Referring to FIG. 1B, the compressor section 26 of the turbine 24 has arotor 42 that is driven, rotated, by the shaft 34 that is typicallydriven by the turbine section 30 of the gas turbine 24, as seen in FIG.1A. The rotor 42 has a plurality of blades or vanes 44. Interposedbetween the rotating blades 44 are stator blades or vanes 46 which areretained by a casing or housing 48 of the compressor section 26 of thegas turbine 24. In keeping with the convention of the industry, the airfoils on the rotor 42 are referred to as rotating blades 44 or blades 44and the air foils on the casing 48 are referred to as stator vanes 46 orvanes 46.

As the shaft 34 rotates, the air is compressed as it moves throughvarious stages of the compressor 26 with the blades 44 and the vanesdirecting the air. The movement of the air places resulting forces onthe rotor blades 44 and vanes 46. These forces cause relative motionbetween the blades 44 and the casing 48 that retains the vanes 46.

In that the blades 44 on the rotor 42 in the embodiment described arerotating in a range of 3000 to 6000 rotations per minute (RPM), therotation of the rotor 42 creates a centrifugal force on the bladestherein preventing movement. Therefore, the vane system 22 is notnecessary with the rotor 42. It is recognized that other rotors rotateat other ranges including at higher ranges.

Referring to FIG. 2, a view of a portion of the casing 48 of thecompressor section 26 is shown. The casing 48 is formed of at least twosemi-circular portions that are fitted together to encircle the rotor 42shown in FIG. 1B. In the embodiment shown, the casing 48 issemi-circular or 180.degree. in curvature. Two units encircle the rotor42. Referring back to FIG. 2, the casing 48 has a plurality of stages 50or rows of stator vanes 46. The vane unit 20 has vane or airfoil 46 thatprojects from the inner surface 52 of the casing 48.

Still referring to FIG. 2, the fourth through eighth stage, 50 d-50 h,of the stator vanes are shown. In conventional compressors, there is adifferent method of attaching stage 1-4, 50 a-50 d, to the housing 48than that of stage 5, 50 e, and higher stages, as discussed below. It isrecognized that the style of the stages varies from gas turbine 24 togas turbine 24.

As seen in FIG. 2 located in proximity to each of the fifth stage 50 estator vanes 46 is a hole 54 to allow air to be drawn from thecompressor section 26 through an air extraction cavity 56 to bearingseals. The stages 50 are referred to both as ordinal number stage orstage cardinal number (i.e., fifth stage or stage five).

The casing 48 has a mounting edge 58, also referred to as a jointsurface, that is secured to a mounting edge 58 on another section ofcasing with fasteners extending through a plurality of holes 60 found onthe edge 58. The spacing of holes 60 are based on various features andmay result in unevenly spaced holes.

FIG. 3 shows the mounting edge 58 of the upper half casing 48 and aportion of the inner surface 52 of the casing 48. The third through theseventh stages 50 c-50 g, stator vanes 46 are shown. A locking bar 62,which is received in a groove 63 as shown in FIGS. 3 and 5B, is used tosecure the stator vanes 46 in stages 5-7. The air extraction cavity 56Is shown below the stage 5 stator vanes 46. As seen in FIG. 2, holes 54are located near the fifth stage stator vanes 46 for drawing air intothe air extraction cavity 56. The fourth stage 50 d, which is shown tothe right of the fifth stage 50 e in FIG. 3, is secured by using a ringand locking method as described below with respect to FIG. 5C.

In the embodiment shown, the vanes 46 for the fifth stage and higherstages in the compressor section 26 are secured to the casing 48 by eachvane 46 being part of the section compressor vane unit 20. Thecompressor vane unit 20, as seen in FIG. 4A, has a base 64 from whichthe airfoil or the vane 46 projects. The base 64 has a pair of mountingedges 65 that are opposite each other and a pair of engaging edges 68for engaging adjacent bases of vane units 20.

The base 64 of the vane unit 20 has a pair of projections 66 forsecuring to the casing 48 as discussed below. The projection 66 extendsfrom each of the mounting edges 65. For those vane units 20 that are forthe fifth stage 50 e, the base 64 has the hole 54 for drawing air intothe air extraction cavity 58. It is recognized that while each stage issimilarly constructed, the individual compressor vane units 20 are sizedfor the respective stage and for factors such as curvature, clearancelength, and width.

FIG. 5A illustrates an enlarged side view of the casing 48 showing thefifth stage 50 e. A plurality of the compressor vane units 20 areassembled in the casing 48 to form the stator vane stage, as seen inFIG. 3. The casing 48 has a plurality of slots 70 for receiving the vaneunits 20. The slot 70 has a pair of side edges 74 which have a groove ora pair of dovetails 76. The square base dovetall 76 holds the vane units20 in place. Each vane unit 20 is allowed to slide into place with thebase 64 received in the slot 70 and the projections 66 received in thegrooves 76. The casing 48 in the embodiment shown has the air extractioncavity 56 that underlies the fifth stage 50 e and is formed by the slot70 and the vane units 20. The air extraction cavity 56 draws air throughthe hole 54 in a base 64 of the vane unit 20 as seen in FIG. 4A.

The vanes in the prior art located above the air extraction cavity 56were more susceptible to relative motion to the casing as discussedabove.

FIG. 5B shows the view of the mounting edge 58, also referred to as ajoint surface, of the casing with the slot 70 for the seventh stage 50g. The vane units 20 for the seventh stage 50 g have a base 64 with apair of projections 66 for securing to the casing 48. The base 64 has arelief space 77 between it and the bottom of the slot 70; the reliefspace 77 aids in the installation and removal. The base 64 does not havea hole through which air passes. A groove 63 for the locking bar 62 asshown.

As indicated above, the first four stages 50 a-50 d of stator vanes areattached using a ring and blade assembly. FIG. 5C shows a ring segment78 that is slid out and away from the casing 48. The ring segment 78receives a plurality of blades 80. (As indicated above, blades that arestationary are typically referred to as stator vanes.) One of theproblems with the existing first stage through fourth stage installationis the method about replacement of a blade 80 when it is damaged in thatthe ring segments 78 need to be hammered out of the slot 70 since it istypical that the ring segment 78 gets bound in the slot 70. In additionto destroying the ring segment 78, there is a risk of damaging othercomponents of the turbine. One of the reasons why the first four stagesare assembled using this blade and ring assembly is that these bladesare larger and have more forces placed on them and therefore need astiffer base mount. The invention as described below allows the vaneunits 20 as improved to be used in the first four stages.

The first four stages use the blade 80 and ring segment 78 method, inconventional compressor as described above, because these vanes whichare longer than those of other stages have more force placed on them.With the vane system 22 as described in further detail below, the ring78 and blades 80 can be replaced by a square base vane unit 20 as shownin FIG. 4A. The use of individual vane units, such as represented byreference numeral 86 as a separation of the ring into multiple vaneunits allows for reduce cost from that of the ring segment and blade.The use of multiple vane units provides for the pinning together of thevane units 20 provides for a stiffer mount.

Referring back to FIG. 4A, each vane unit 20 has the airfoil vane 46that extends upwards radially inward towards the shaft 34 of the rotorsection 42 when in the compressor section 26 from the base 64. Theairfoil vanes 46, stator vanes, are interposed between the rotor blades44. The base 64 has a projection 66 on each of the two opposing mountingedge 65 to be received by the groove 76 in the side edge 74 of the slot74 of the casing 48 to retain the vane unit 20 in place, as describedabove. In addition, the base 64 of each of the vane units 20 has a pairof blind holes 94 machined into the base 64. The blind holes 94 are eachlocated on one of the engaging sides 68 of the base 64, the sides nothaving the projections 66. A spring pin 96 is inserted into the blindhole 94 in one square base 64 and into the corresponding hole 94 in thebase 64 of the adjacent vane unit 20.

While a square base 64 for the vane unit 20 is shown, it is recognizedthat other shapes may be desired dependent on the number, size and shapeof the airfoil. For example, the base 64 can have a rectangular shape ora parallelogram shape.

FIG. 4B shows a plan view of the spring pin 96. The spring pin 96 is aslotted spring pin 142 that is a headless hollow cylindrical tube 144having a longitudinal slot 146 down the entire length. The ends 148 arechamfered to aid installation. The spring pin 96 is selected to acontrolled outside diameter slightly greater than the blind hole 94 inwhich it will be installed. Compressed as it is installed, the pin 96applies continuous pressure towards the sides of the hole wall. Thepressure provides tension in a radial manner to prevent looseningcreated by vibration or shock.

In a preferred embodiment, the spring pin 96 is made of Nickel StainlessSteel. The pin has a length of 1 inch, an outer diameter of in a rangeof 0.385 to 0.395 inches in an uncompressed state, and a wall thicknessof 0.077 inches. The chamfer length is a range of 0.016 to 0.095 inches.A spring pin 96 such as described above is sold by Spirol PrecisionEngineered Products of Danielson, Conn. as 1 inch length ⅜ CorrosionResistant Steel AISI420.

FIG. 6 shows an exploded view of a pair of vane units 20 with theinterposed spring pin 96. In one embodiment, the spring pin 96 has astiffness to provide enough frictional force to resist motion; or dampvibration (reducing wear) if static friction is overcome. The process ofjoining vane units 20 by the spring pin 96 is continued until a vanering 88, as seen in FIG. 2 extends from one edge 58 of the casing 48 asshown in FIG. 2 to the other edge 58 of the casing 48, for example, 180°in a preferred embodiment. The size of the vane ring 88 is dependent onseveral factors including the curvature of the casing and thereforealternative arc sizes are also possible, depending on the requirementsof the particular compressor design. While it is possible to link a vaneunit 20 of the lower casing 48 to the adjoining vane unit 20 of theupper casing 48, with the spring pin 96 it is not necessary.

FIG. 7 illustrates two vane units 20 for the fifth stage 50 e that areattached. The bases 64 are attached by the spring pin 96. While thepinned vane units 20 are shown removed from the casing 48, the vaneunits 20 are connected in the slot in the casing 48. In that the vaneunits 20 are for the fifth stage, the base 64 of each unit 20 has a hole54 through which air is drawn.

A gap 98 is created between the bases 64 of the vane units 20. The gap98 is created because of the square base 64 of the vane unit 20 incombination with the curvature of the slot 70. While the bases can betapered, the taper would increase the cost of each vane unit 20 becauseof machining. Furthermore, it is not desired to have a tight fit becauseof thermal expansion.

In installing the vane units 20 with the airfoil blades 46, the firstvane unit 20 is positioned halfway between the edges 58 of the casing48. The first vane unit 20 has the two blind holes 94. The second vaneunit 20 has a spring pin 96 that is to be received by one of the bladeholes 94 on the first vane unit. FIG. 8 shows a sectional view of a pairof vane units 20 in the slot 70 of the casing 48. The slot 70 has theside edge 74 with the groove 76. The slot 70 includes the air extractioncavity 56 that underlies the vane units 20.

The casing 48 shown is the upper portion and includes an air extractionhole 100 at top dead center (TDC). The vane units 20 are placed in theslot 70 in the casing 48 and are built up from the center of the casing48. As the vane units 20 are placed into the slot 70, the vane system 22has a plurality of shims 102, which are interposed between vane units20, to space the vane units 20 such that the last vane unit's engagingedge 68 is within an allowable clearance with the edge 58 of the casing48. In the prior art, the shims 102 as seen in FIG. 9 have a pair oftabs 104 which are received in the groove 76 on the side edge 74 of theslot 70 to retain the shim in position.

In the prior art, with the vane units and the shims moving because ofaerodynamic forces on the airfoils, the tabs 104 wear away and the shims102 can protrude into the flow path as seen in FIGS. 10A and 11. Theexample shown of the protruding shim 110 does not exist in the vanesystem 22 of the invention which the remainder of FIG. 11 shows. Theprotruding shims 110 can cause rotating blade stimulation and flowblockage. In addition, the shims can work their way totally out of theslot 70 in the casing 48 and enter into the air stream and cause bladeforeign object damage (FOD) on downstream blades and vanes. FIG. 10Bshows a gap 108 between two airfoil blades 46 because of loss of shimsand movement of vane units.

Referring to FIG. 11, a sectional view of the casing 48 with the vanesystem 22 in proximity to the edge 58 of the casing 48 is shown.Interposed between the last three vane units 20 are shims 102 secured bythe pin 96 between the adjacent vane units 22. The shims 102 space thebases 64 of the vane units 20 so that the last vane unit's 20 engagingedge 68 is within an allowable clearance with the edge 58 of the casing48.

FIG. 12 shows a side perspective view of a shim 102 carried by the pin96 adjacent to a pair of vane units 20. The shim 102 has a hole 106through which the spring pin 96 extends from the blind hole 94 of one ofthe bases to the blind hole 94 of the adjacent base. The spring pin 96prevents the shim 102 from moving out of position and possibly enteringthe air stream and hitting a blade or vane down stream.

It is recognized that while a pin, a spring pin 96, is shown anddescribed above, between every adjacent vane unit 20, that the lack of aspring pin 96 at sporadic locations will not substantially reduce theperformance. For example, in a preferred embodiment there is no springpin spanning between the two casing portions 48.

In addition, while the above has shown vane units 20 each having asingle airfoil or blade, it is recognized that a unit may have aplurality of airfoils. The number of airfoils in a unit is dependent onthe size and the shape of the airfoil and the curvature of the casing48. While not limited to this number, generally 5 to 7 airfoils to asingle base is the maximum. It is also recognized that increasing thenumber of airfoils on a single base increases the overall cost of theunit for various reasons including machining, forging, investmentcasting, or welding the unit. Furthermore, the multiple airfoilsincrease the difficulty of accessing all sides of the airfoils on oneunit. In addition, the curvature of the base adds to the cost.

The vane system 22 is described with respect to the compressor section26 of the gas turbine 24. The compressor section 26 operates in atemperature range of ambient temperature to approximately 600° F.

The turbine section 30, also referred to as the hot section, operatesand can operate at temperatures in excess of 800° F. and higher. Springpins will soften and will not function at the high temperature of theturbine section. In addition, there needs to be some movement to allowfor thermal expansion. However, slip pins can be used to link severalvane units together to allow movement between adjacent pinned units.

In order to install the vane system 22 with the vane units 20 and thespring pin 96, existing vane units need to have a hole 94 located oneither side, the engaging edge 68, of the base 64, that is the edge thatdoes not have the projection 66. FIG. 13 shows a fixture 112 fordrilling pin holes 94 in the base 64 of the vane unit 20. The channel114 has a pair of grooves 115 similar to the grooves 76 of the sideedges 74 and the slot 70 as seen in FIG. 5A. The groove 115 receives theprojection 66 of the base 64. The groove 115 is set at an angle suchthat when the fixture 112 is placed on a machining device, the holeplaced in the base 64 of the vane unit 20 is of the proper angle for thecurvature of the slot 70 in the casing 48. For example, in oneembodiment, the casing receives eighty two (82) vane units 20 betweenthe two halves. Each hole is drilled at 2.195° incline relative to beingparallel to the top and bottom base 64 in this preferred embodiment. Thefixture 112 has a channel 114 that receives the base 64 of the vane unit20.

A pin 116 projects from the base 118 of the channel 114 to position thebase 64 of the stator vane unit 20 relative to the top 120 of thefixture 112. The positioning of the hole on the base is done byalignment on a milling machine of the drill bit with the hole 122 in thefixture 112. The head of the milling machine is translated a specificdistance such as an inch from that alignment hole 122 to position thedrill bit for drilling the hole in the base 64.

The installation of the vane units 20 in the casing 48 can be done withthe rotor section 42 in place in the compressor section 26. In order todo this, the installer needs to reach the vane units 20.

FIG. 14A shows the front view of an assembly tool 130 and FIG. 14B showsa side view of the tool 130 that can be used in the installation of thevane unit 20. The vane units 20 are placed into the slot 70 in thecasing 48 by sliding the first vane unit 20 down so that the first vaneunit 20 is located at the bottom dead center in the casing 48 such thatthe unit is equally distant from the edges 68 of the casing. A pluralityof the assembly tools 130 are slid in such that the lowest one engagesthe vane unit 20 from one side.

The assembly tool 130 has a main portion 132 that has a curvaturesimilar to the slot 70 in the casing 48. The main portion 132 of theassembly tool 130 has a width and thickness such that it extends betweenthe two grooves 76 in the side edges 74 of the slot 70. Located at eachend of the main portion 132 is a contact block 134 which has a greaterthickness. The contact block 134 has a width that when received by theslot 70 in the casing 48 extends approximately to the side edges 74 ofthe slot 70, that is of a width approximate to the base 64 of the vaneunit 20. The assembly tools 130 can be linked together using a cablingthat extends between a hole 136 located in the main portion 132 of theassembly tool 130.

A second vane unit 20 is slid into the slot 70 in the casing 48 on theside not having the assembly tools 130. Additional assembly tools 130are used to move the second vane unit 20 into engagement with the firstvane unit 20. The assembly tool 130 has a series of lines or scribelines 138 such that the assembly tool 130 that extends from the slot 70above the edge 58 of the casing 48 can be used to determine if thesecond vane unit 20 is in full engagement with the first vane unit 20.When the second vane unit 20 is initially slid in, the spring pin 96rests against the base 64 of the first vane unit 20, but does not enterthe blind hole 94. The installer can look at the scribe lines 138 on theassembly tool 130 and determine to what line 138 on the assembly tool130 the edge 58 of the casing 48 must be aligned to by driving theassembly tool 130 in order to install the second vane unit 20 properly.

The assembly tools 130 are then removed from the slot 70 and the nextvane unit 20 is slid into the slot 70. The assembly tools 130 are thenreinstalled to position the vane unit 20.

When the vane unit 20 approaches the edge 58 of the casing 48, the lastseveral vane units 20 are slid into the slot 70 in the casing 48 withoutspring pins 96 interposed between the vane units 20. It is determinedhow many shims 102 are required to result in the engaging edge 68 of thebase 64 of the last vane unit 20 being within an allowable clearancewith the edge 58 of the casing 48. After the proper number of shims 102are determined by a “dry fitting,” the vane units 20 are removed fromthe slot 70 in the casing 48 and are installed using spring pins 96 thatin addition to holding the vane units 20 secure, retain the interposedshims 102 such as shown in FIG. 11. The shims 102 have a hole 106through which the spring pin 96 passes. The tabs 104 of the shims 102are received in the groove 76 on the side edge 74 of the slot 70 in thecasing 48.

When the first side is completed by building up the vane units 20 to theedge 58 of the casing 48, the plurality of assembly tools 130 that wereslid into the other side are removed and the vane units 20 are built uptowards the other edge 58 of the casing 48.

In a preferred embodiment, the assembly tool 130 has a length of 12inches and a width of 2.6 inches excluding the contact blocks 134. Themain portion 130 has a thickness of an eighth (⅛) of an inch and aradius of curvature of 32 inches. The contact blocks 134, which arewelded onto the main portion 132 of the tool 130, each have a length of2 inches and a height and depth of a quarter (¼) of an inch.

The two holes 136 in the main portion 132 of the assembly tool 130 havea diameter of ⅝ of an inch. The center of each of the holes 136 isspaced from the main portion 132 and contact block 134 interface by 2inches. The holes 136 are for securing assembly tools 130 together withcable or assisting for retrieving the assembly tools. It is recognizedthat the size of the tool 130 is dependent on various factors such asthe size of the slot 70 and the curvature of the casing 48.

It is recognized that the assembly tool 130 is designed to fit therespective casing and slot that would be receiving the respective vaneunit 20 during installation. For example, the assembly tool dimensionsgiven above are for a GE 7EA gas turbine engine.

FIGS. 15A-15C show the reaction forces on the vane unit of the prior artwith the forces including the aerodynamic loading and the interactionbetween the vane unit and casing. FIGS. 16A-16C show the reaction forceson the vane unit 20 of the invention with the forces including the airloading, the interaction between the vane unit 20 and the casing 48, andthe spring pin 96 interaction.

The vane unit according to the invention can be used to retrofitexisting gas turbines that have square base compressor vanes. Theretrofit will solve the wear problem in the existing gas turbines

The spring pin 96 is used for ease of modification and low cost. It isrecognized that other mechanisms such as bolting, welding, brazing, canbe used to fasten the vane units 20 together.

By use of the vane system with the vane units 20 and the spring pin 96,axial and circumferential tip movement of the vane 46, which possiblycould result in interference with a blade 44 on the rotor section 42, isreduced. The measurement of movement of the free edge of the airfoilwent from 0.063 inches to approximately zero (0). There is no freemovement of the vane unit 20.

By use of the spring pin 96 between the bases 64 of the vane unit 20,the vane unit 20 forms a rigid unit of plurality of vane units whereinthe edges of the projection 66 are not the engaging surface that getworn away. But rather, the centered portion of the projection 66 is theportion that is in firm contact within the groove 76 in the side edge 74of the slot 70. Therefore there is no movement between the bases 64 ofthe vane unit 20 and the casing.

In addition, with the use of this spring pin 96 extending through theshim 102, the migration of the shim 102 into the flow stream isprevented. As indicated above, the existing gas turbine 24 embodimentsuse the vane units 20 with projections 66 from the base 64 received ingrooves 76 in the side edges 74 of the slot 70. Therefore, the vane unitsystem 22 with the vane unit 20 and spring pin 96 does not require newvane units unit stator blades 46. The vane units are removed andmodified with the blind hole 94 to receive the pin 96. The task ofdetermining if the set of blades are good operationally or have theproper tip clearance has already been done when the blades wereinitially produced for this compressor section 26 of the gas turbine 24.

By pinning the vane unit 20 with the spring pin 96 and the vane system22 together, the vane units are held simply so that any previous wearprior to use of the invention on the forward edge and aft edge of theprojection 66 is not of a concern. Therefore, the owner of the gasturbine 24 is not required to machine out the slot 70 in the casing 48wherein the operator needs to take the gas turbine out of commissionwhile the slot is machined out and a patch ring is installed having theslot 76 within it.

The use of the vane system 22 allows the overhaul of the current gasturbines 24 to be within the normal time constraints and not affectothers' work.

While the above disclosure describes the retrofitting of an existing gasturbine 24, it is recognized that the main system may be used on new gasturbine designs. For example, FIG. 5C shows the configuration with thering and blade used for the first four stages 50 a-50 d of current gasturbine designs. The reason for this different design for the first fourstages is because the first four stages have larger airfoils or vanesand therefore more aerodynamic force and thus require more stability.With the vane system 22, the individual vane units 20 are linkedtogether and the reason for having a different design for stages 1-4 isnot required. Therefore, the vane system 22 as described above may beused in the first four stages. This will result in lower cost. The vaneunit 20 can have an airfoil 46 secured to the base 64 or a separateblade unit 80 attached to the ring segment unit or vane base.

As indicated above, the vane system 22 can be formed by pinning togethervane units 20 with a pin 96 using a prior art vane unit 20 with theaddition of a pair of blind holes 94. It is recognized that othermethods of coupling vane units 20 to each other can be done. Forexample, the vane unit can have a projection on one engaging edge thatis receivable in a hole in an adjacent engaging edge. Anotheralternative is an adhesive pad that mounts between and to the twoadjacent engaging edges. Other components and apparatus are a tongue andgroove arrangement.

The above discusses the issues of where the stator vane units 20 becomeloose or shims 102 work their way loose and into the air flow stream.The vane unit system according to the invention in addition can solveadditional problems on the compressor section 26 of the gas turbine 24.As seen in FIG. 18, certain compressors 156 have an air extraction slot158 that has a 360.degree. opening onto the inner surface 52 of thecasing 48. This results in a cantilever portion of the casing retaininga stage of stator vanes such as the tenth stage in a GE Frame 5 GasTurbine. The cantilever portion has a tendency to crack away from theremainder of the casing and has a potential to enter the air stream anddestroy downstream blades and vanes.

The tenth stage of the compressor with the air extraction slot is shownin FIGS. 18 and 19. The vane system according to the invention has aplurality of vane units 162, spring pins 96 and at least onehook-capturing bracket 164. The hook-capturing bracket 164 captures thecracked casing hook 166 at the edges and prevents further crackpropagation.

The conventional method was to remove the rotor 42 from the casing 48and machine out a casing hook 166. A new ring is installed and machinedto have the slot 70 with groove 76.

FIG. 19 shows a casing 48 with a horizontal joint or edge 58. The vaneunit 162 that is adjacent to the edge 58 in addition has a blind hole174 for a spring pin 96 for connecting to the remaining vane units 162.The base 172 of the vane unit 162 has a threaded hole 168 through itsbottom. The bracket 164 is used to secure the casing hook portion 166 ofthe casing 48. A bolt 170 extends through the bracket 164, the casing 48and into the threaded hole 168 of the vane unit 162.

FIG. 20 is a top view of the vane unit 162. The base 64 of the vane unit162 shows the pair of blind holes 174 in hidden line and the threadedhole 168 for the retaining bolt 170 is shown. in this embodiment, theblind holes 174 are shifted from the centerline. It is recognized thatthe location of the blind holes 174 can be shifted. While the embodimentabove describes use of two brackets 164, it is recognized thatadditional brackets 164 can be included. The upper casing 48 which isseparated from the rotor 42, allows placement of multiple brackets. Withrespect to the lower casing 48, if the rotor 42 is removed, additionalbrackets can be installed. The bracket 164 is bent to secure the bolt170.

FIG. 21 shows an exploded view of a pair of vane units 180 of analternative embodiment. Each vane unit 180 has a groove 182 on oneengaging edge 68 and a tongue 184 on the other engaging edge 68. Thetongue 184 of one vane unit is received by the groove 182 of theadjacent vane unit 180 to form the vane units 180 together in a ringunit. This provides enough frictional force to resist motion; or dampvibration (reducing wear) if static friction is overcome. The process ofjoining vane units 180 continues until a vane ring extends from one edge58 of the casing 48 to the other edge 58 of the casing 48.

In addition to spring pins, other types of pins can be used. Otherpotential pins include a coiled spring pin, an interference fit pin,such as a groove pin. With an interference fit pin such as a groovedpin, however, the vanes could not be used again with the same sized pinbecause the hole in the base would have been distorted and gouged fromremoving the pin. Likewise, a coiled compression spring could be placedin the base holes and compressed as the bases are slid together. Thiswould provide vibration damping and limited movement of the base in thecasing groove. All these devices could work to varying degrees ofsuccess relative to the slotted spring pin.

The claims should not be read as limited to the described order orelements unless stated to that effect. Therefore, all embodiments thatcome within the scope and spirit of the following claims and equivalentsthereto are claimed as the invention.

What is claimed:
 1. A compressor comprising: a casing having at leastone slot, the slot having a pair of side edges, each side edge having agroove; a plurality of vane units, each vane unit having a base andairfoil vane projecting from the base, the base defining a pair ofholes; and a pin extending between the holes in, and joining, adjacentbases of the vane units for forming a ring segment from a plurality ofvane units.
 2. The compressor of claim 1 further comprising at least oneshim interposed between a pair of adjacent vane units, the shim defininga hole through which the pin between the adjacent vane units extends. 3.The compressor of claim 1 wherein the pin is a slotted spring pin havinga hollow cylindrical tube defining a longitudinal slot.
 4. Thecompressor of claim 3 wherein the cylindrical tube has chamfered ends.5. A compressor comprising: a rotor having a plurality of blades; acasing for encircling the rotor a plurality of vane units, each vaneunit having a base and at least one airfoil vane projecting from thebase; the casing defining at least one slot for retaining the vanes; anda coupling device extending between and joining adjacent bases of thevane units for forming a ring segment from a plurality of vane units tostiffen the airfoil vanes.
 6. The compressor of claim 5 wherein thecoupling device is at least one pin extending between holes defined inadjacent bases.
 7. The compressor of claim 6 wherein the pin is aslotted spring pin having a hollow cylindrical tube defining alongitudinal slot.
 8. The compressor of claim 5 wherein the couplingdevice is a projection on one base received by a hole defined on theadjacent base.
 9. The compressor of claim 5 wherein the coupling deviceis a groove on one vane unit for receiving a tongue on an adjacent vaneunit.
 10. A compressor comprising: a rotor having a plurality of blades;a casing for encircling the rotor; a plurality of vane units, each vaneunit having a base and at least one airfoil vane projecting from thebase; the casing defining at least one slot for retaining the vanes andan air extraction slot, the air extraction slot underlying the slot anddefining a casing hook; a coupling device extending between adjacentbases for forming a ring segment from a plurality of vane units tostiffen the airfoil vanes; and at least one bracket carried by one vaneunit engaging the casing hook.
 11. The compressor of claim 10 whereinthe coupling device is at least one pin extending between holes definedin adjacent bases.
 12. The compressor of claim 10 wherein the pin is aslotted spring pin having a hollow cylindrical tube defining alongitudinal slot.
 13. The compressor of claim 12 wherein thecylindrical tube has chamfered ends.
 14. The compression of claim 10further comprising at least one shim interposed between a pair ofadjacent vane units, the shim defining a hole through which the pinbetween the adjacent vane units extends.
 15. The compressor of claim 10wherein the bracket is secured by a fastener extending through thecasing and to the base of the vane unit.